IMPEDANCE OF REDOX REACTIONS AT A POLYPYRROLE MEMBRANE

A Pt sheet or a free-standing polypyrrole (PPy) membrane has been stud ied in a Double Submerged Impinging Jet (DSU), in the presence of elec trolytes containing redox couples. Impedance diagrams relative to PPy may be analysed as the result of two parallel paths involving (i) conv ective diffusion of the redox species in solution, electron transfer a t the polymer/electrolyte interface, electron transport within the fil m and (ii) migration of non-electroactive ions in solution, ion transf er at the polymer/electrolyte interface, ion transport within the film . For a fast redox couple and a low ionic conductivity of the membrane , PPy explicitly shows an electrocatalytic effect with respect to Pt.